Controlled Alternator Decoupling for Reduced Noise and Vibration

Development of a novel alternator pulley for reduction of engine noise and vibration is described in detail. The sources of noise and vibration resulting from interaction of the alternator's apparent inertia with the speed variation of the engine crankshaft are discussed and quantified as they relate to decoupling of this vibration from the alternator rotor. Present approaches to improving the noise and vibration as well as reducing the wear and stress on accessory drive belts are discussed as background to the discussion of the controlled decoupling pulley. The new pulley is described in detail, including its working principal, part configuration details, and both static and dynamic characteristics compared with competitive pulleys, followed by details of the development phases. Finally, the test and evaluation methods for functionality and durability are described and test results for the controlled decoupling pulley are presented, organized according to the pulley development phases to illustrate the progress from initial concept to production intent prototype evaluation. The controlled decoupling approach to alternator pulley design reduces accessory drive belt tension variation by at least 90 percent and maintains that improvement throughout the pulley's life. This approach to engine noise and vibration reduction as well as accessory drive belt life improvement is immediately applicable to aftermarket replacement part requirements as well as to OEM applications.